In recent years, there is an increasing demand for reduction in size and thickness of portable electronic equipment. To reduce the size or thickness of electronic equipment, it is effective to use a flexible substrate in the electronic equipment, so that the variation in component layout can be increased.
For example, by using a flexible substrate for an electronic module, increased variation in component layout can be realized, and simultaneously, the electrode (connection terminal) provided on the module substrate can be directly joined to the electrode (connection terminal) provided on the main circuit board or the like of the electronic equipment (see Patent Literature 1). The electronic module can thus be connected to the main circuit board without a conductor wire for connection, improving the space efficiency. Moreover, a broken wire and the like are unlikely to occur, improving the reliability in connection between the components.
In the case of directly joining the electrode on the module substrate to the electrode on the main circuit board as mentioned above, a reinforcement portion containing a thermosetting resin is typically formed around the junction where the electrodes are joined. Specifically, an uncured resin supplied between the module substrate and the main circuit board is heated via the module substrate or main circuit board and cured, thereby to form a resin reinforcement portion comprising cured resin.
Conventionally, in joining a plurality of electrodes of the electronic module to a plurality of electrodes of the main circuit board, a heating tool having a pressing surface whose area is equal to or larger than that of a connection region including those electrodes is used to join the electrodes to each other.